(Phys.org)—Similar to the way that a conventional magnetic resonance imaging (MRI) machine uses large magnets to generate 3D images, physicists have developed a proposal for a quantum nano-MRI machine that would use the ...

(Phys.org)—Scientists have fabricated a superlattice of single-atom magnets on graphene with a density of 115 terabits per square inch, suggesting that the configuration could lead to next-generation storage media.

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their ...

Just like in normal road traffic, crossings are indispensable in optical signal processing. In order to avoid collisions, a clear traffic rule is required. A new method has now been developed at TU Wien to provide such a ...

Bacterial resistance does not come just through adaptation to antibiotics, sometimes the bacteria simply go to sleep. An international team of researchers is looking at compounds that attack bacteria's ability to go dormant ...

Water is vital to life on Earth and its importance simply can't be overstated—it's also deeply rooted within our conscience that there's something extremely special about it. Yet, from a scientific point of view, much remains ...

A team of University of Illinois researchers has discovered the existence of hot atomic hydrogen (H) atoms in an upper layer of Earth's atmosphere known as the thermosphere. This finding, which the authors report in Nature ...

In nanotechnology control is key. Control over the arrangements and distances between nanoparticles can allow tailored interaction strengths so that properties can be harnessed in devices such as plasmonic sensors. Now researchers ...

Atom

The atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen-1, which is the only stable nuclide with no neutron). The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other, forming a molecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it has a positive or negative charge and is an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determine the isotope of the element.

The name atom comes from the Greek ἄτομος/átomos, α-τεμνω, which means uncuttable, something that cannot be divided further. The concept of an atom as an indivisible component of matter was first proposed by early Indian and Greek philosophers. In the 17th and 18th centuries, chemists provided a physical basis for this idea by showing that certain substances could not be further broken down by chemical methods. During the late 19th and early 20th centuries, physicists discovered subatomic components and structure inside the atom, thereby demonstrating that the 'atom' was divisible. The principles of quantum mechanics were used to successfully model the atom.

Relative to everyday experience, atoms are minuscule objects with proportionately tiny masses. Atoms can only be observed individually using special instruments such as the scanning tunneling microscope. Over 99.9% of an atom's mass is concentrated in the nucleus, with protons and neutrons having roughly equal mass. Each element has at least one isotope with unstable nuclei that can undergo radioactive decay. This can result in a transmutation that changes the number of protons or neutrons in a nucleus. Electrons that are bound to atoms possess a set of stable energy levels, or orbitals, and can undergo transitions between them by absorbing or emitting photons that match the energy differences between the levels. The electrons determine the chemical properties of an element, and strongly influence an atom's magnetic properties.